The present invention relates generally to the presentation of tests to a subject at different viewing distances, and more particularly to the presentation of eyesight tests, and especially those for checking the visual acuity of the subject.
Visual acuity tests are typically presented to the subject whose eyesight is to be checked at a single predetermined distance which corresponds, for example, to distant vision for the subject.
It would, however, also be interesting to be able to check the visual acuity of the subject for near vision, and intermediate vision, particularly for biotechnological purposes.
Such visual acuity testing at different distances typically involves successively placing the acuity test indicia at different distances from the subject between the shortest viewing distance and the longest viewing distance.
If in conjunction with such a change in viewing distances it is desirable to maintain the test indicia at the same visual acuity irrespective of the viewing distance it is normally necessary to have as many sets of different size test indicia as there are potential different viewing distances.
Indeed to maintain the visual acuity constant the visual angle under which the subject views the test images must remain constant and therefore the sizes of the test indicia increase proportionally to the viewing distance at which they are presented to the subject.